A distance measurement apparatus is known which can be used for measurement of the three-dimensional shape of a commodity or a component. In recent years, with the automation of production in a factory, a distance measurement apparatus which is small in size and cheap in cost is required to be capable of measuring at a high speed in a non-contact manner. Thus, a distance measurement apparatus (for example, see Japanese Unexamined Patent Application Publication No. Hei 6-213658) that measures a distance through a triangulation method using laser light and a distance measurement apparatus (for example, see Japanese Unexamined Patent Application Publication No. 2014-102072) that measures a distance through a fight time measurement method using laser light are developed.
FIG. 1 is a diagram illustrating a distance measurement apparatus 7 that measures a distance through the triangulation method.
In the distance measurement apparatus 7, a controller 71 controls to drive a semiconductor laser 73 via a current driver 72 at a constant current. A measurement object 9 is irradiated with laser light output by the semiconductor laser 73 via a condenser lens 74. The laser light reflected by the measurement object 9 makes a spot imaged on a photodiode 76 (position detection element) through a light receiving lens 75. The position of the spot changes depending on displacement amount of the laser light in an optical axis direction.
The controller 71, through a drive module (not shown), measures the displacement amount of the spot on the photodiode 76 while causing the distance measurement apparatus 7 and the measurement object 9 to move relatively in the vertical direction shown in FIG. 1 orthogonal to the optical axis of the laser light. In this way, the controller 71 can measure the displacement amount of the measurement object 9 in the optical axis direction to measure the surface shape of the measurement object 9.
However, there is a problem in the distance measurement apparatus 7 using the triangulation method that the range of a measurable distance to the measurement object 9 is extremely narrow.
FIG. 2 is a diagram illustrating a distance measurement apparatus 8 that measures a distance through the fight time measurement method.
In the distance measurement apparatus 8, a controller 81 controls to drive a semiconductor laser 83 at a constant current via a current driver 82. After laser light output by the semiconductor laser 83 is collimated by a collimating lens 84, part of the laser light is taken out by a half mirror 85 and the laser light of this part is received by a photodiode 86.
When the distance measurement apparatus 8 measures flight time of the laser light from a moment when the laser light is output to a moment when the laser light is reflected by the measurement object 9 and returns, the controller 81 starts to measure the flight time at a timing when the photodiode 86 receives the laser light.
The measurement object 9 is irradiated with the laser light passing through the half mirror 85. The laser light reflected by the measurement object 9 is received by the photodiode 88 through a light receiving lens 87. The controller 81 terminates the measurement of the flight time of the laser light at a timing when the photodiode 88 receives the laser light.
The controller 81 can measure the distance from the semiconductor laser 83 to the measurement object 9 by calculating the flight time of the laser light.